RESULTS OF U.S. FOREST SERVICE STEREOTRIANGULATION BRIDGING ON VIRGINIA HIGHWAY PHOTOGRAMMETRIC TEST PROJECT

THE FOREST SERVICE OF THE U. S. DEPARTMENT OF AGRICULTURE IS CONSTANTLY STRIVING TO IMPROVE THE QUALITY OF THE SURVEYS IT MAKES BY PHOTOGRAMMETRIC METHODS. THE TESTS DESCRIBED IN THIS REPORT WERE CONDUCTED USING THE USUAL METHODS AND PROCEDURES. THE REPORT PERTAINS TO FOUR BASIC FACTORS WHICH AFFECT THE QUALITY OF PHOTOGRAMMETRICALLY MADE MEASUREMENTS' /A/ IDENTIFICATION OF GROUND CONTROL /HORIZONTAL AND VERTICAL/ POINTS ON THE AERIAL PHOTOGRAPHY, /B/ MOVEMENT OF THE AERIAL CAMERA DURING NEGATIVE EXPOSURE, /6/ SCALE OF THE AERIAL PHOTOGRAPHY, AND /D/ QUANTITY OF GROUND CONTROL. INCLUDED ARE TABULATIONS SHOWING RESULTS OF THE BRIDGES /EXTENSION OF BASIC GROUND CONTROL BY PHOTOGRAMMETRIC METHODS/ USING VERTICAL PHOTOGRAPHY TAKEN WITH TWO DIFFERENT AERIAL CAMERAS, TWO TYPES OF CONTROL IDENTIFICATION, FOUR SCALES OF PHOTOGRAPHY, AND VARIOUS SPACINGS OF GROUND CONTROL. THESE RESULTS ARE BASED ON THE PHOTOGRAMMETRIC MEASUREMENT AND ELECTRONIC COMPUTATION OF 50 BRIDGES. ALSO PRESENTED IS AN OUTLINE OF PROCEDURES TO BE FOLLOWED FOR THE LOCATION AND DESIGN OF HIGHWAYS BASED ON SURVEYS ACCOMPLISHED BY PHOTOGRAMMETRIC METHODS, AS WELL AS CONCLUSIONS BASED ON THESE TESTS. /AUTHOR/